Mobile telephones are widely used because of their ability to communicate at a variety of locations. FIG. 1 depicts a typical prior art mobile telephone communication system 100. The system comprises a mobile telephone 110, which transmits an uplink radio signal 111 to a base station 120. The base station 120 transmits a downlink radio signal 112 to the mobile telephone. The base station 120 is also connected to a telephone equipment 130 through a connection 122, which is usually part of the public switched telephone network (PSTN). The telephone equipment 130 can include other telephones, automated answering units or a modem connected to a computer, and a server 410. The system 100 provides a point-to-point two-way connection between the mobile telephone 110 and the telephone equipment 130.
A frequently-used accessory for mobile telephones is a hands-free kit (HFK). FIG. 2 depicts a typical prior-art HFK 200 used in conjunction with the mobile telephone 110. The kit includes a male jack 210, which is coupled to a female jack 220 attached to a housing of the mobile telephone 110. The HFK 200 further includes a cable 230 and an earpiece 240. The earpiece 240 is coupled to the cable 230 and is adapted to generate an audible sound signal in response to an electrical signal received from the mobile telephone 110 through the male jack 210 and the female jack 220 and the cable 230.
The HFK 200 further includes a microphone 250. The microphone 250 is also coupled to the cable 230 and is adapted to generate an electrical signal in response to a detected sound signal. The signal generated by the microphone 250 is conveyed to the mobile telephone 110 through the cable 230 and the male jack 220 and the female jack 210. As an advantage, the user of a mobile telephone can wear the HFK 200, thus freeing the user's hands to perform other tasks.
As described in the related application, the mobile telephone 110 can use simulated voice activity to communicate wirelessly with a receiver that detects an envelope of the radio transmission. It would be advantageous to generate such simulated voice activity without modifying existing mobile telephones. A typical application for this communication technique locates, identifies, or authenticates the mobile telephone.
This application is typically realized through a connection to an authentication server 410 connected to the telephone equipment 130. It would also be advantageous to realize such a connection without having to modify existing mobile telephones, wireless networks, and wireless communications air interface standards.
It is desired to provide an external device for a mobile telephone so that the mobile telephone is enabled for the functionality described above, without requiring modifications to the mobile telephone.